Sheikh Hamad bin Khalifa Al Thani is used to basking in the limelight. But when the emir of Qatar arrived in Gaza on Tuesday – the first Arab leader in years to visit the impoverished coastal strip – he was hailed for breaking its siege, demonstrating his country's huge and growing influence in the Middle East.

Palestinians rolled out the red carpet for the emir as his black Mercedes bumped along a rutted main road that he has promised to rebuild, past white and maroon Qatari flags, the song Thank You, Qatar playing endlessly on local radio and TV.

Sheikh Hamad flew to Egypt and crossed the border into Gaza, a move billed as breaking the blockade in force since the Islamists of Hamas took power in 2007. It also underlined the ability of the tiny, fabulously rich Gulf state to punch above its weight internationally.

He arrived with 90 tonnes of aid and pledged $400m (£250m) to invest in housing and infrastructure to replace property damaged in the 2008-09 war with Israel.

Flanked by his wife, the elegant and high-profile Sheikha Mozah, he spoke to a large crowd at Gaza's Islamic University, the biggest event of a six-hour stay.

The last head of state to visit the strip was King Abdullah of Jordan, who went there in 1999 for talks with then Palestinian president, Yasser Arafat.

Predictably, the brief royal visit was the top news item on al-Jazeera, the satellite TV channel owned by the emir's family and which has been an unabashed and influential cheerleader for the uprisings of the Arab spring from Tunisia to Syria.

Qatar's ambitious move was a stunning boost for Hamas, shunned by Israel, the US and western countries as a terrorist organisation. Ismail Haniyeh, its deposed prime minister, called it a historic event that had broken the "unjust blockade".

"The visit gives Hamas legitimacy in the Arab world and internationally," said Mkhaimar Abusada, an independent analyst at Gaza's al-Azhar university. It was further striking evidence that Qatar, whose per-capita income is now the highest in the world, is in effect using its enormous oil and gas riches and close ties to Islamist organisations to expand its regional influence in the wake of its involvement in the uprisings against Libya's Muammar Gaddafi and Bashar al-Assad in Syria.

"The emir is confirming that Qatar is the principal supporter of the Muslim Brotherhood takeover in Egypt and everywhere else," said Ahmed Asfahani, the respected al-Hayat newspaper columnist. "Qatar is using the Brotherhood to promote its own interests. It also shows that Qatar is trying to replace Iran as a major player on the Palestinian issue."

Observers in the region also see the visit in part as a reward to Hamas for ending its support for Assad. Until a few months ago, the movement's exiled leadership was based in Damascus, helping bolster Syria's credentials as a key member of the "axis of resistance" confronting Israel, along with Iran and Hezbollah in Lebanon.

But its veteran leader, Khalid Mish'al, decamped to Doha. And Haniyeh came out in open support of the right of the Syrian people to oppose Assad.

Mahmoud Abbas, the western-backed Palestinian president and leader of Fatah, had let it be known from his headquarters in the West Bank town of Ramallah that he was furious about the visit, which plays into the hands of his bitterest rival. "Nobody's happy about it," said one Palestinian source. "It definitely makes a statement. And of course there is a track record of Arab regimes playing into intra-Palestinian politics."

The PLO welcomed any help with reconstruction in Gaza, but called on "all Arab brethren to … use their leverage to ensure an end to the division and the policy of creating a separatist entity in the Gaza Strip, as [this] principally serves the Israeli agenda." There is also an unspoken fear of eroding the claim of Abbas's Palestinian Authority to be the sole representative of the Palestinians.

Israel angrily condemned the Qatari visit as well. "We find it weird that the emir doesn't support all of the Palestinians but sides with Hamas over the Palestinian Authority [in the West Bank] which he has never visited," said its foreign ministry spokesman, Yigal Palmor. "The emir has chosen his camp and it is not good."

In the background, it is possible to discern a new pattern of relations emerging in a political landscape transformed by the Arab spring in which a key player is the Egyptian president, Mohamed Morsi, a leader of the Muslim Brotherhood.

In the era of Hosni Mubarak, Qatar was often at loggerheads with Egypt, which, like many other Arab governments, hated al-Jazeera and saw it as a disruptive instrument of Qatari policy. Even now, Doha is being more radical than Cairo. Formally, Egypt considers Abbas as the representative of Palestinians and Gaza as under PA authority (or that the end state of Palestinian reconciliation should be a West Bank and Gaza united under PA control). The emir called publicly for efforts to promote reconciliation between the Palestinian rivals to confront Israel. "It will be interesting to see if Qatar is now going to play a more active role in mediating between Hamas and Fatah, or even Hamas and Israel," said Abusada.

Doha has won admiration and irritation in equal measure in the Middle East and beyond. Uniquely, it maintains cordial, if low-key, relations with Israel as well as Iran, hated by other Gulf Arabs. It is also home to a large US air base. Its wealth speaks eloquently. In September, it announced plans to invest $18bn over five years in Egypt. Its aid also helped reconstruction in south Lebanon after the 2006 war between Hezbollah and Israel. At that time, the emir worked closely with Assad, only to turn against him when the Syrian uprising began 19 months ago. In Libya last year, Qatar bankrolled the anti-Gaddafi rebels but channelled resources through Islamist brigades only to face criticism later that it was behaving in a manipulative manner. Now Qatar has become a key supporter of the armed Syrian opposition, amid growing concern in the west that the weapons it pays for are reaching jihadi-type groups rather than democratic forces.

Among its other accomplishments, Qatar is to host the 2022 World Cup, having defeated bidders including the US and Japan. Following intense lobbying it also recently managed to join La Francophonie – the 57-member bloc of French-speaking nations – as an associate member. French is barely spoken in Qatar but it insists it is committed to promoting use of the language.